1999 abstracts

Statistical Model of the Splashing Products Produced by Liquid Drop Impact on a Solid Surface

Mario Trujillo,
University of Illinois

Droplet splashing occurs in a wide variety of applications, including spray painting processes, injection of liquid fuel in internal combustion engines, fire suppression systems, and many others. The subject is definitely not new and has received attention by numerous researchers for over a century. Due to its complexity, however, characterized by large deformations over very small time scales, propagations of instabilities in the emerging liquid crown and sheet, formation of jets along the rim, and subsequent jet break, the study of the splashing phenomena is far from complete.

Our interests in this area are the determination of the velocity and size characteristics of secondary droplets created during splashing, as well as the calculation of quantities that described the overall splashing event (e.g. the amount of energy lost due to viscous dissipation). With an emphasis towards automotive applications, the single droplet splashing study presented here provides a foundation for the investigation of spray impingement on containment walls, where thousands of droplets collide against a solid surface.

Our approach is based on describing the products of splashing in terms of a joint probability density function (jpdf) of an assumed form, and solving this jpdf by applying the conservation laws to the splashing process. Drop size calculations from this model are compared to experimental drop size data yielding acceptable agreement. The distribution of incident droplet energy among the kinetic and surface energy of the secondary droplets, the residual film surface energy, and the time integrated viscous dissipation are calculated as a function of the incident Weber number and the impingement angle. Information is also obtained on the incident angle dependence of the impact forces.